Preparing analytical samples by fusion for X-ray fluorescence (XRF), atomic absorption (AA) or inductively induced plasma (ICP) analysis typically includes mixing a sample with a flux material, such as lithium tetraborate or lithium metaborate, and heating the mixture to a temperature sufficient to melt the flux material and dissolve the sample to form a homogeneous fused mixture. The homogeneous fused mixture is generally subsequently poured either into a preheated mold to obtain a glass disk suitable for XRF analysis, or into a solution-containing container, such as a beaker, to obtain a solution suitable to be analyzed by AA, ICP or another wet chemistry analysis.
The mixture is typically heated in crucibles provided in a heat furnace (such as a fluxer) to temperatures of approximately 1000° C. At such temperatures, energy losses in the form of heat radiation radiating from the crucibles can be significant. It can thus be desirable to reduce the energy required for heating the mixture.
Further, if the temperature of the homogeneous fused mixture exceeds 1100° C. for a certain time period, some volatile elements such as sodium, chlorine and/or fluorine can start to evaporate from the sample, thereby affecting the subsequent analyses. For at least this reason, it can be desirable to measure and/or control the temperature of the mixture. Existing solutions include measuring the temperature of the mixture by directly measuring the temperature of the crucible using either a type R thermocouple or a pyrometer. However, both the type R thermocouple and the pyrometer can lead to an increase in manufacturing costs for the manufacturer, as well as maintenance costs for the user. Furthermore, the use of a pyrometer is often impractical, as the temperature reading from the pyrometer directly depends on the emissivity value of the crucible surface, which typically changes over time with normal laboratory use, thereby affecting the temperature measurements.
The preparation of analytical samples by fusion still poses a number of challenges.